Add 125g (4oz) caster sugar to a pan with 200ml (7fl oz) water. Bring to the boil, then turn down and simmer for 5 mins or until you have a thin syrup. Remove and cool completely.
Carefully rinse or (if they’re very ripe and too delicate to wash) pick clean 500g (1lb) raspberries and purée in a food processor, along with the juice of half a lemon.
Using a wooden spoon (or, alternatively, a ladle), press the raspberry mixture through a fine wire sieve so you have a smooth, slightly pulpy juice. Discard all of the seeds.
Mix the cooled syrup with the fruit and pour into a shallow plastic box or baking dish – ideally, one that is 20x30cm (8x12in). Freeze for 2 hours, or until partially solid.
Break up the mixture with a fork, scraping down the length of the tub. Return to the freezer and repeat the process twice more, at half hour intervals, then let it freeze a final time.
When you’re ready to serve, transfer the tub to the fridge for 30 minutes so that the granita can soften up a little, then spoon it into 4-6 small glasses or bowls.
Freezing and defrosting instructions
Can be frozen and kept in the freezer for up to three months. When ready to serve, transfer the tub to the fridge for 30 minutes so that the granita can soften up a little.